1. Field of the Invention
The present invention relates to a completing emergency calls placed from telephone devices connected to a data network.
2. Description of the Related Art
Traditional phone systems include local carriers and long distance carriers. Local carriers connect calls within a given local area, while long distance carriers carry calls between the local carriers. The telephone lines from a home or office connect directly to a wire center, which is often referred to as a central office. The central office has one or more switches, which route or direct telephone calls from one destination to another.
Telephone numbers typically include an area code, and a seven digit telephone number. The seven digit telephone number includes a three digit central office number, and four digit central office extension. The three digit central office number directs calls to a particular central office. Once the call reaches the desired central office, the four digit extension directs the call to a line that is served by that central office. Area codes are typically used for long distance phone calls, as discussed below.
Local telephone calls within a small area are often completed within a single central office. In this configuration, calls within the same area are served by the same central office. The central office connects the incoming call to the destination number. If the area is larger however, communication with a second central office may be necessary. The two central offices are typically connected by a trunk, which is a line between the central offices. The destination receives the call from the first central office and then directs it to the appropriate destination, based on the dialed phone number.
Each area code, as mentioned above, corresponds to a particular group of central offices. When a user dials an area code and then the seven digit telephone number, the central office analyzes the dialed number. If the dialed number is located within the Local Transport and Access Area (LATA), then the call is directed to the appropriate central office. A LATA, or local calling area, is typically a contiguous geographic area. If the dialed number is outside of the LATA, the local central office checks its database to determine which long distance company the user has selected for making the call. The local central office then switches the call to lines that are connected to the long distance company's nearest switch, often referred to as a point of presence (POP). Once the long distance company receives the call, it analyzes the phone number and routes the call across the long distance network to the POP that is closest to the called number. That POP routes the call back to a local central office that is near the destination phone, which then completes the call as described above.
The local and long distance companies incur costs for the equipment, switching calls, and maintaining their equipment. All of these costs are eventually passed on to the consumer. Because local calls involve one or two switching stations owned by one company, the costs of a local telephone call are typically low. Typically, a consumer pays a fixed fee for a unlimited amount of local calls. However, because long distance calls are transferred from the local telephone company, to a long distance carrier, and then back to a local telephone company, the cost of a long distance call is greater than a local call. Typically, long distance calls are charged by the minute. However, rates vary depending on a number of factors, such as the number of switches between the originating and destination numbers and taxes. For example, long distance calls between countries may be higher than long distance calls within a given country.
A continuing need exists for a method and apparatus that is capable of reducing the costs associated with long distance telephone calls. One solution that meets this need is the use of virtual numbers to complete calls over a data network, as described in U.S. patent application Ser. No. 10/774,689, filed Feb. 10, 2004 and entitled “Method and Apparatus for Placing a Long Distance Call Based on a Virtual Phone Number”, which is hereby incorporated by reference in its entirety. However, a problem that arises with this solution is the placement and completion of emergency calls. Typically, such calls are placed by dialing “911” and are completed to a public safety answering point (PSAP) based on the physical location from which the call was placed. In the conventional public switched telephone network (PSTN), the determination of the physical location from which a call is placed is quite simple, as the telephone devices at each location are hard-wired to switching equipment in a central office. However, with calls placed over a data network, the telephone devices are typically not directly connected to the call switching and routing equipment in the network. Thus, a need arises for a technique by which emergency calls placed from telephone devices connected to a data network may be completed to the appropriate PSAP.